IS-95与CDMA2000技术的发展

目前,CDMA在成为第三代通信系统最主要的无线接入技术后,技术上出现了突习猛进,本文对现有的CDMA技术IS－95与CDMA2000技术作出比较,简要地介绍了CDMA2000的技术特点和其向3G平滑过度的演进过程,进一步探讨IS－95和CDMA2000在今后的发展趋势。     

cdmaOne和cdma2000标准体系及其演进

本文简要描述了基于IS95的CDMA系统和cdma2000系统的标准体系结构及其演进过程，其中包括无线接口、A接口、移动应用部分、智能网、短消息、定位和分组数据等部分。     

HRPD空中接口技术(A版本)

HRPD(HighRatePacketData)空中接口标准(IS-856)是cdma2000标准家族的一员,该技术在高速数据传输方面进行了优化,能够很好地支持移动通信网络中各种类型的数据分组应用。其0版本的标准于2000年颁布,标志着高速数据业务的可实现化。而颁布不久的空中接口标准A版本(IS-856-A)则是弥补了0版本的诸多不足,既对每层协议都有相应的增强又新增了不少协议以提高性能。就HRPD空中接口标准A版本进行介绍,着重介绍其物理层和高层协议对新业务和服务质量(QoS)的支持。     

Modeling and Performance Evaluation of 3G CDMA Networks with Beamforming

The second generation (2G) code-division multiple access (CDMA) IS-95A cellular network has been deployed for almost ten years. Although the system design rules and operating procedures for voice services are well established and understood, these rules and procedures need to be re-examined in light of several technology innovations. These innovations include the launch of third generation (3G) cdma2000 1× high-rate data services and the new research results in interference cancellation, antenna array and multiple-input multiple-output (MIMO) technologies.We have built a 3G cdma2000 1× cellular simulator, which simulates the physical layer using MATLAB and networking layers using OPNET Modeler, to investigate various design issues of cdma2000 1× networks. This paper explores the use of a simple beamforming model and investigates the effectiveness of deploying antenna array techniques in cdma2000 1× networks. The capacity improvement for CDMA networks using antenna array techniques is evaluated under different deployment scenarios (voice versus data services and various number of antenna elements). Based on the performance evaluation results it is proposed to utilize beamforming as one of the elements in quality of service (QOS) provisioning for data services and to couple antenna arrays with dynamic soft handoff threshold adjustment for further improvement in the system capacity.This paper was presented in part at IEEE 60th Vehicular Technology Conference (VTC), Los Angeles, CA, USA, Sep. 26–29, 2004.     

cdma2000反向信道的分析

根据给出的cdma2000系统的反向信道基本构成和技术特点,将RC1(即IS-95CDMA)和RC3两种最为常用的无线配置方法进行了对比,并阐述了cdma2000在扩频调制、功率控制、变速率传输、差错控制以及随机接入方法等方面的改进,而这些改进明显提高了cdma2000的通信性.     

从A接口看IS-95到cdma2000 1x的演进

文章主要从A接口的角度,阐述CDMA从IS-95到cdma20001x的演进过程,着重从协议体系结构和业务功能两方面,分别对IS-95系统和cdma20001x系统的A接口进行详细描述,最后简要介绍CDMAA接口的发展趋势。     

Adaptation techniques in wireless packet data services

Today's cellular systems are designed to achieve 90-95 percent coverage for voice users (i.e., the ratio of signal to interference plus noise must be above a design target over 90 to 95 percent of the cell area). This ensures that the desired data rate which achieves good voice quality can be provided “everywhere”. As a result, SINRs that are much larger than the target are achieved over a large portion of the cellular coverage area. For a packet data service, the larger SINR can be used to provide higher data rates by reducing coding or spreading and/or increasing the constellation density. It is straight-forward to see that cellular spectral efficiency (in terms of b/s/Hz/sector) can be increased by a factor of two or more if users with better links are served at higher data rates. Procedures that exploit this are already in place for all the major cellular standards in the world. In this article, we describe data rate adaptation procedures for CDMA (IS-95), wideband CDMA (cdma2000 and UMTS WCDMA), TDMA (IS-136), and GSM (GPRS and EDGE)     

无线分组数据自适应技术

对于分组数据业务来说 ,如果用户有一个良好的连接 ,则蜂窝的频谱效率和数据速率都会得到长足的提高 ,全世界所有的蜂窝标准都利用了这一点来进行数据速率自适应 ,文中就以下几种系统描述数据速率自适应过程 :CDMA (IS - 95 ) ,宽带CDMA (CDMA2 0 0 0和UMTSCDMA) ,TDMA (IS - 136 )和GSM (GPRS和EDGE) ,并探讨一些尚待解决的问题     

Link layer retransmission schemes for circuit-mode data over the CDMA physical channel

In the last few years, wide-area data services over North American digital (TDMA and CDMA) cellular networks have been standardized. The standards were developed under three primary constraints: (i) compatibility with existing land-line standards and systems, (ii) compatibility with existing cellular physical layer standards that are optimized for voice, and (iii) market demands for quick solutions. In particular, the IS-95 CDMA air interface standard permits multiplexing of primary traffic (e.g., voice or circuit data) and secondary traffic (e.g., packet data) or in-band signaling within the same physical layer burst. In this paper, we describe two radio link protocols for circuit-mode data over IS-95. The first protocol, Protocol S, relies on a single level of recovery and uses a flexible segmentation and recovery (FSAR) sublayer to efficiently pack data frames into multiplexed physical layer bursts. We next describe Protocol T, that consists of two levels of recovery. Protocol T has been standardized for CDMA circuit-mode data as IS-99 (Telecommunications Industry Association, 1994). We provide performance comparisons of the two protocols in terms of throughput, delay and recovery from fades. We find that the complexity of the two level recovery mechanism can buy higher throughput through the reduced retransmission data unit size. However, the choice of TCP (and its associated congestion control mechanism) as the upper layer of recovery on the link layer, leads to long fade recovery times for Protocol T. The two approaches also have significant differences with respect to procedures and performance at handoff and connection establishment. This revised version was published online in June 2006 with corrections to the Cover Date.     

A new base station receiver for increasing diversity order in a CDMA cellular system

A new base station receiver is proposed and analyzed for a code-division multiple-access (CDMA) cellular system. The proposed receiver can achieve remarkable diversity gain by increasing diversity order with reasonable cost and complexity. From the numerical results, it is confirmed that the proposed receiver structure can be a practical solution for enhancing reverse-link capacity and improving performance in CDMA cellular system operations. The result in the letter can find its applications to legacy IS-95/cdma2000 1x base stations with simple modifications.     

Potentials of smart antennas in CDMA systems and uplinkimprovements

An overview of the application of smart antennas in DS-CDMA systems, including IS-95 and IS-2000, is presented. Since CDMA systems are interference-limited, adaptive antenna arrays have great potential for improving the performance of such systems in terms of capacity, coverage, and quality of service, In this paper, we study the multiple-access interference that affects a CDMA system, and we describe how smart antennas can be implemented in an IS-2000-based mobile communications system. When smart antennas are used at the base station to transmit in narrow beams, the interference on the downlink is reduced, and C/I is improved. This, in turn, increases the system capacity on the downlink or, alternatively, the quality of service is improved. Such gains will prove very beneficial for asymmetric high-speed data applications, requiring much higher bit rates on the downlink than on the uplink. By reducing the base-station receiver's sensitivity, smart antennas can boost the capacity of the reverse link. Results are presented that outline how this reduction can be employed by the system designer on the uplink to increase capacity, reduce the mobile transmit power, or effect a tradeoff between capacity improvement and coverage or range extension under different system-loading scenarios     

cdma2000 1X网络混合业务环境下载波配置方法的探讨

介绍了cdma2000 1X语音、数据业务对资源的占用情况,引入了最大平均吞吐量的概念来衡量载波的处理能力,总结了一套关于cdma2000 1X混合业务网络资源配置的方法。     

码分多址（CDMA）技术和公用空中接口综述

本文主要讨论数字移动通信中扩频码分多址技术，阐明了ＣＤＭＡ体制的优越之外，分析了ＣＤＭＡ的关键技术，全面介绍了ＣＤＭＡ系统设计的基本原则和ＩＳ－９５－Ａ空中接口标准的含义。     

软切换对cdma2000 1x数据业务的影响及优化策略

降低软切换比例在目前CDMA网络中具有重要的意义和紧迫性,本文通过分析CDMA软切换对系统资源占用及对cdma2000 1x数据业务性能的影响,提出降低软切换的几种方法。实际案例说明,降低软切换比例在CDMA网络中取得了容量和质量的明显提高。     

An analytical model for reverse data channel scheduling techniques in cdma2000 1xEV‐DO

Efficient utilization of bandwidth and high data rates have a great impact on the performance of wireless networks. The cdma2000 1xEV‐DO standard provides high‐speed wireless data services to mobile subscribers based on CDMA technology. In this paper, we study the bandwidth utilization for the 1xEV‐DO packet mode standard. In particular, we develop an analytical model for lowest‐rate‐first, highest‐rate‐first priority scheduling techniques, and two round‐robin fair scheduling techniques over the reverse data channel in cdma2000 1xEV‐DO. For these four scheduling techniques, the distribution of the mobile stations (MSs) among the possible data rates is modeled as a Markov process. An analytical expression for the steady state system throughput is derived from the steady state distribution of the above Markov process. The developed model is validated through simulations. Copyright © 2008 John Wiley & Sons, Ltd.     

An overview of CDMA evolution toward wideband CDMA

Third-generation mobile radio networks, often dubbed as 3G, have been under intense research and discussion recently and will emerge around the year 2000. In the International Telecommunications Union (ITU), third generation networks are called International Mobile Telecommunications-2000 (IMT-2000), and in Europe, Universal Mobile Telecommunications System (UMTS). IMT-2000 will provide a multitude of services, especially multimedia and high-bit-rate packet data. Wideband code division multiple access (CDMA) has emerged as the mainstream air interface solution for the third-generation networks. In Europe, Japan, Korea, and the United States, wideband CDMA systems are currently being standarized. This article provides a comprehensive introduction to wideband CDMA. It also provides a review of the wideband CDMA air interface proposals including WCDMA in Europe and Japan, cdma2000 in the United States, and wideband CDMA in Korea.     

Beyond 3G: wideband wireless data access based on OFDM and dynamicpacket assignment

The rapid growth of wireless voice subscribers, the growth of the Internet, and the increasing use of portable computing devices suggest that wireless Internet access will rise rapidly over the next few years. Rapid progress in digital and RF technology is making possible highly compact and integrated terminal devices, and the introduction of sophisticated wireless data software is making wireless Internet access more user-friendly and providing more value. Transmission rates are currently only about 10 kb/s for large cell systems. Third-generation wireless access such as WCDMA and the evolution of second-generation systems such as TDMA IS-136+, EDGE, and CDMA IS-95 will provide nominal bit rates of 50-384 kb/s in macrocellular systems. This article discusses packet data transmission rates of 2-5 Mb/s in macrocellular environments and up to 10 Mb/s in microcellular and indoor environments as a complementary service to evolving second- and third-generation wireless systems. Dynamic packet assignment for high-efficiency resource management and packet admission; OFDM at the physical layer with interference suppression, space-time coding, and frequency diversity; as well as smart antennas to obtain good power and spectral efficiency are discussed in this proposal. Flexible allocation of both large and small resources also permits provisioning of services for different delay and throughput requirements     

cdma2000 1x无线网络规划方法

由于无线频带资源有限,因此在无线网络规划中应着重考虑如何提高频谱效率。描述了cdma20001x无线网络规划过程,cdma20001x的基本特点,并比较了cdma20001x系统与IS-95系统在无线网络规划上的差异。     

Adaptation of CDMA Soft Handoff Thresholds Using Fuzzy Inference System

This paper proposes a new procedure to adjust soft handoff thresholds dynamically by using fuzzy inference system. This algorithm is compared with IS-95A and IS-95B/cdma2000 soft handoffs. The aims are to increase the thresholds at high traffic loads in order to release the traffic channel for supporting more carried traffic, and to decrease the thresholds at low traffic loads in order to give high quality of traffic channel. The inputs of the proposed algorithm are the number of remaining channels of each base station and the number of active pilots in active set of each mobile station. The output is the new soft handoff thresholds. In the fuzzy inference module, the triangular membership function, the max-min composition, and the weighted average formula defuzzification are selected. By comparison of all performance indicators among three algorithms, soft handoff using fuzzy inference tends to give higher performance than those of IS-95A and IS-95B/cdma2000 soft handoffs at high traffic loads and at lower soft handoff thresholds while the quality of traffic channel is still acceptable. Moreover, the wider soft handoff window size of the proposed algorithm gives high carried traffic and low blocking probability but lower quality of traffic channels. In addition, the adaptive soft handoff window size can give lower blocking probability while still keep acceptable quality of traffic channels.     

High data-rate packet communications for cellular networks usingCDMA: algorithms and performance

The advantages of code division multiple access (CDMA) for cellular voice have become well known, and IS-95-based systems have now been widely deployed. Attention is now focused on higher data-rate packet services for cellular systems. Although many packet multiple access schemes have been studied over the years, researchers have often studied single cell performance and ignored reuse. Moreover, direct sequence spread spectrum (DSSS) has been considered unsuitable for high data-rate packet multiple access since spreading limits the permitted data rates, DSSS requires large overhead (preambles) for acquisition and requires closed-loop power control. In this paper, we describe a scheme for high data-rate packet service using CDMA that addresses all of the above problems and has been standardized in Revision B of IS-95. A low rate fundamental code channel is maintained that eliminates the need for long preamble and provides closed-loop power control. Reuse is managed by the infrastructure through a “burst-level” admission control based on load and interference-level measurements at the base stations and mobiles. We report on the feasibility of such a burst-mode packet data service for cellular CDMA networks. The focus is not only on the performance of high data-rate users, but also on the impact on voice users sharing the CDMA band. We propose a multitiered performance analysis methodology consisting of a mix of static simulations, dynamic simulations at different time scales, and analytic methods to address the various feasibility issues: impact on coverage; capacity; power control; and effectiveness of burst admission algorithms. Based on the current study, we can conclude that the proposed approach is well suited for third-generation wideband CDMA systems being considered for standardization throughout the world